Process for the preparation of tetrabromobisphenol-A

Abstract

Tetrabromobisphenol-A is produced in a bromination process where no bromine or only a very small proportion of bromine is fed to the reactor. In the process aqueous hydrobromic acid, is the sole source or a major source of the bromine. In the process there are at least three concurrent continuous feeds to the reactor. One is composed of bisphenol-A and/or underbrominated bisphenol-A and a water-miscible organic solvent. The second is gaseous hydrogen bromide or preferably, aqueous hydrobromic acid, and the third is aqueous hydrogen peroxide. Optionally a small additional continuous feed of bromine can be employed. The feeds are proportioned to maintain a liquid phase containing (i) from above about 15 to about 85 wt % water, based upon the amount of water and water-miscible organic solvent in such liquid phase, and (ii) an amount of unreacted bromine that is in excess over the stoichiometric amount theoretically required to convert the bisphenol-A and/or underbrominated bisphenol-A to tetrabromobisphenol-A. The tetrabromobisphenol-A continuously forms as a solids phase in a yield of at least about 90% based on bisphenol-A and/or underbrominated bisphenol-A fed. The reaction mass is agitated and/or refluxed to maintain a substantially uniform slurry in the reactor. An amount of the slurry is continuously removed so that the volume of the contents of the reactor remains substantially constant.

That which is claimed is:  
     
       1. A process for the production of tetrabromobisphenol-A, which process comprises: 
       a) concurrently feeding to a reactor (i) a first continuous feed stream composed of bisphenol-A and/or underbrominated bisphenol-A and a water-miscible organic solvent, (ii) a second continuous feed of gaseous hydrogen bromide and/or aqueous hydrobromic acid, and (iii) a third continuous feed of aqueous hydrogen peroxide, at relative rates that maintain in the reactor a reaction mass having a liquid phase containing from above about 15 to about 85 wt % water, the wt % being based upon the amount of water and water-miscible organic solvent in the liquid phase of the reaction mass;  
       b) during at least a substantial portion of the concurrent feeding in a), maintaining the temperature of the reaction mass within the range of about 30 to about 100° C.;  
       c) during at least a substantial portion of the concurrent feeding in a), providing said continuous feeds at relative rates (i) that maintain in the liquid phase of the reaction mass an amount of unreacted bromine that is in excess over the stoichiometric amount theoretically required to convert the bisphenol-A and/or underbrominated bisphenol-A to tetrabromobisphenol-A, and to continuously form during substantially all of the time the feeding in a) is occurring, a precipitate comprised mainly of tetrabromobisphenol-A, and (ii) that result in a yield of precipitated tetrabromobisphenol-A during substantially all of the time the feeding in a) is occurring of at least about 90% based on the amount of the bisphenol-A or underbrominated bisphenol-A or combination thereof fed up to that point in time; and  
       d) during at least a substantial portion of the concurrent feeding in a), withdrawing from the reactor a mixture of precipitated tetrabromobisphenol-A and a potion of the liquid phase of the reaction mass, such that the volume of the contents of the reactor remains substantially constant during at least a substantial portion of the concurrent feeding in a).  
     
     
       2. A process of claim  1  further comprising agitating the reaction mass during at least a substantial portion of the concurrent feeding in a) to thereby maintain substantially the entire reaction mass substantially uniform in composition during at least a substantial portion of the concurrent feeding in a). 
     
     
       3. A process of claim  1  wherein the water-miscible organic solvent is a water-miscible alcohol, carboxylic acid, nitrile, or ether which is not cleaved in the reaction mass. 
     
     
       4. A process of claim  1  wherein the water-miscible organic solvent is at least one alcohol containing up to 4 carbon atoms in the molecule. 
     
     
       5. A process of claim  1  wherein the water-miscible organic solvent is ethanol. 
     
     
       6. A process of claim  1  wherein the water-miscible organic solvent is methanol. 
     
     
       7. A process of claim  1  wherein the concurrent feeds in a) are at relative rates that maintain in the reactor a reaction mass having a liquid phase containing from about 30 to about 85 wt % water, the wt % being based upon the amount of water and water-miscible organic solvent in the liquid phase of the reaction mass. 
     
     
       8. A process of claim  1  wherein the concurrent feeds in a) are at relative rates that maintain in the reactor a reaction mass having a liquid phase containing from about 30 to about 70 wt % water, the wt % being based upon the amount of water and water-miscible organic solvent in the liquid phase of the reaction mass. 
     
     
       9. A process of claim  1  wherein the weight ratio of said organic solvent to bisphenol-A and/or underbrominated bisphenol-A being fed to the reactor and being maintained in the reactor is within the range of from about 1:1 to about 10:1. 
     
     
       10. A process of claim  1  wherein the weight ratio of said organic solvent to bisphenol-A and/or underbrominated bisphenol-A being fed to the reactor and being maintained in the reactor is within the range of from about 3:1 to about 5:1. 
     
     
       11. A process of claim  1  wherein during at least a substantial portion of the concurrent feeding in a), said temperature is maintained within the range of from about 50 to about 100° C. 
     
     
       12. A process of claim  1  wherein the first continuous feed stream consists essentially of bisphenol and ethanol, and wherein the reaction mass is maintained at reflux temperature. 
     
     
       13. A process of claim  12  wherein the second continuous feed stream consists essentially of a solution of about 20 to about 80 wt % of H 2 O 2  in water, and wherein the third continuous feed stream consists essentially of a solution of about 20 to about 50 wt % of HBr in water. 
     
     
       14. A process of any of claims  1 - 13  wherein no elemental bromine is being fed into said reactor. 
     
     
       15. A process of any of claims  1 - 13  wherein elemental bromine is being fed into said reactor at a substantially constant rate and in quantity such that the mole ratio of Br 2  to HBr being fed does not exceed about 0.5:1. 
     
     
       16. A process for the production of tetrabromobisphenol-A, which process comprises: 
       a) providing a steady-state liquid phase reaction system to which at least a first feed composed of bisphenol-A and/or underbrominated bisphenol-A and a water-miscible organic solvent, a second feed composed of gaseous hydrogen bromide and/or aqueous hydrobromic acid, and a third feed composed of aqueous hydrogen peroxide, are being continuously fed and in which there is being continuously formed a tetrabromobisphenol-A precipitate by the bromination of bisphenol-A and/or underbrominated bisphenol-A with an excess of bromine over the stoichiometric amount theoretically required to produce tetrabromobisphenol-A, and in which  
       1) all of the bromine in said steady-state liquid phase reaction system is formed in situ by reaction between the HBr and the H 2 O 2 , or  
       2) a portion, but no more than 50 mole percent, of said bromine is continuously fed into said system as bromine, with the balance of said bromine being formed in situ by reaction between the HBr and the H 2 O 2 ,  
        such that tetrabromobisphenol-A is being formed continuously in a yield of at least about 90% based on the amount of the bisphenol-A and/or underbrominated bisphenol-A already fed;  
       b) agitating and/or refluxing the reaction system so as maintain a substantially uniform slurry within the reaction system; and  
       c) continuously separating from the reaction mass, an amount of the substantially uniform slurry to continuously maintain the reaction system at substantially constant volume.  
     
     
       17. A process of claim  16  wherein all of the bromine in said steady-state liquid phase reaction system is formed in situ by reaction between the HBr and the H 2 O 2 . 
     
     
       18. A process of claim  16  wherein a portion, but no more than 50 mole percent, of said bromine is continuously fed into said system as bromine, with the balance of said bromine being formed in situ by reaction between the HBr and the H 2 O 2 . 
     
     
       19. A process of any of claims  16 - 18  wherein said first feed is composed of bisphenol-A and/or underbrominated bisphenol-A and ethanol, and wherein in b) said reaction system is refluxed. 
     
     
       20. A process of any of claims  16 - 18  wherein said first feed consists essentially of bisphenol-A and ethanol, wherein the second continuous feed stream consists essentially of a solution of about 20 to about 80 wt % of H 2 O 2  in water, wherein the third continuous feed stream consists essentially of a solution of about 20 to about 50 wt % of HBr in water, and wherein in b) said reaction system is refluxed. 
     
     
       21. A bromination process in which tetrabromobisphenol-A is produced with little or no bromine being fed to the bromination reaction mass, said process comprising maintaining at least three concurrent separate continuous feeds to a reaction mass having a liquid phase composed of a water-miscible organic solvent and water, said three feeds being composed of (1) bisphenol-A and/or underbrominated bisphenol-A and the water-miscible organic solvent, (2) gaseous hydrogen bromide and/or aqueous hydrobromic acid, and (3) aqueous hydrogen peroxide, said feeds being proportioned and the reaction mass being maintained at a temperature such that under steady-state reaction conditions (a) bromine and water are being continuously formed in situ by oxidation of HBr by H 2 O 2 , (b) tetrabromobisphenol-A is being continuously formed as a solids phase in an overall yield of at least about 90% based on the amount of the bisphenol-A and/or underbrominated bisphenol-A already fed, (c) hydrogen bromide is being continuously formed in situ as a co-product of the bromination that is forming the tetrabromobisphenol-A, (d) an excess amount of unreacted bromine is continuously present in the liquid phase of the reaction mass, and (e) the amounts of water being fed and being generated in situ continuously maintain a water content in the liquid phase of the reaction mass that is high enough to cause the tetrabromobisphenol-A to continuously precipitate from the liquid phase at the same time tetrabromobisphenol-A is being continuously formed. 
     
     
       22. A process of claim  21  wherein a portion, but no more than 50 mole percent, of the bromine in the liquid phase of the reaction mass is bromine being continuously fed into said system as bromine, with the balance of said bromine being formed in situ by reaction between the HBr and H 2 O 2  being fed. 
     
     
       23. A process of claim  21  or  22  further comprising mechanically agitating and/or refluxing the reaction mass to maintain substantial uniformity in the reaction mass. 
     
     
       24. A process of claim  21  or  22  further comprising (i) mechanically agitating and/or refluxing the reaction mass to maintain substantial uniformity in the reaction mass, and (ii) continuously separating a portion of the substantially uniform reaction mass from the remainder of the reaction mass. 
     
     
       25. A process of claim  21  or  22  further comprising (i) mechanically agitating and/or refluxing the reaction mass to maintain substantial uniformity in the reaction mass, (ii) continuously separating from the reaction mass, an amount of the substantially uniform reaction mass to continuously maintain the reaction mass at substantially constant volume.